Conventional nail polish hardens because its solvent evaporates. Gel polish hardens because UV light triggers a chemical reaction. That single difference explains almost everything you experience at the salon: why gel resists chips for weeks, why lacquer peels in days, and why gel removal demands a long acetone soak.
Introduction: The Science Behind Your Manicure
Painting your nails looks simple. The chemistry underneath is not. Polymerisation, solvents, photoinitiators — these are lab terms that describe exactly what happens on your nail plate.
Every polish you can buy falls into one of two chemical families. Conventional lacquer, the type in most drugstore bottles, is a polymer dissolved in solvent, as the chemistry education site Compound Interest explains. Gel polish is a reactive mixture of acrylate compounds that solidifies under ultraviolet light. Both produce a glossy, colored film. The route they take to get there is completely different — and that route determines how the manicure performs.
Conventional Lacquer: Drying by Evaporation
Traditional polish starts with nitrocellulose, a cellulose polymer nitrated to precise nitrogen levels — in nail lacquer, typically the RS type at around 10.7–12% nitrogen, according to formulation chemist Absar Khan. At that nitrogen content, nitrocellulose dissolves readily in ester and ketone solvents.
The liquid you brush on is mostly that dissolved polymer in a solvent such as ethyl acetate or butyl acetate. Once spread on the nail, the solvent simply evaporates into the air. What is left behind is a solid polymer film. No new chemical bonds form. The polish hardens only because the liquid carrier leaves.
Because nothing reacts, the film can be undone by the same kind of chemistry that made it: drop the polymer back into a suitable solvent and it dissolves again. Adhesive polymer resins in the formulation help the film grip the keratin of your nail and add gloss.
UV Gel Polish: Curing by Polymerization
Gel polish takes the opposite approach. Instead of waiting for liquid to escape, you supply energy and force the mixture to become something new.
The backbone of a gel formula is a set of urethane acrylate or epoxy acrylate oligomers, paired with reactive diluent monomers such as HEMA or isobornyl acrylate, per Khan's formulation analysis. The crucial ingredient is the photoinitiator: a compound that splits apart under UV or LED exposure to generate free radicals. Those radicals kick off a chain-growth polymerisation across the acrylate double bonds throughout the gel.
Applied in layers and exposed to UV light, the polish does not dry — it cures. The oligomers and monomers link into a rigid, cross-linked polymer network in seconds. The structure of that network, and especially its crosslink density, determines the cured film's hardness, flexibility, and chemical resistance.
